Electromagnetically operated tool



A ril 20, 1965 R. H. DOYLE ETAL 3,179,866

ELECTROMAGNETICALLY OPERATED TOOL Filed Dec. 22. 1961 I I I I I I I l II I l I l I I I I I I I I I I I I INVENTORS E/ch ARD H. DOYLE;

BY LEROY M HERMAN/J AA/D JOSEPH l-/. NABE/Z United States Patent3,179,866 ELEC'I'ROMAGNETICALLY OPERATED TOOL Richard H. Doyle, MountProspect, Le Roy N. Hermann,

Saint Charles, and Joseph S. Naber, Wheeling, Ill., assignors toFastener Corporation, Franklin Park, Ill., a corporation of IllinoisFiled Dec. 22, 1961, Ser. No. 161,727

9 Claims. (Cl. 318-125) This invention relates to a portable tool and,more particularly, toa self-contained tool in which all of thecomponents for controlling the electrical operation of the tool arecarried on the tool. 7

The need for portable tools capable of performing the many differenttypes of material working operations has long been recognized, and manydifferent approaches have been tried in an attempt to provide tools thatare capable of easy manual manipulation while supplying the power orenergy necessary to perform the desired operation. These approaches havebeen used in such varied devices as staplers, nailers, staking tools,riveters, punches, chisels, scarfing tools, stud drivers and hog ringtools. The primary difficulty is to be able to supply sufficient drivingpower without increasing the weight and size of the tool to the point atwhich it becomes so unwieldy and cumbersome that it cannot be easilyhandled by one hand of an operator.

One common expedient used in designing portable tools is to provide adevice in which the work is performed in a series of power strokes sothat the power required in any given one of the operations is greatlyreduced. This approach is embodied in the use of rotating orreciprocating pneumatic and electric motors to apply increments ofenergy over an extended period of time. However, in addition to theobvious deficiency of the greater length of time required to completethe operation, some of the types of operations performed by the toolsdescribed above are suchthat they should be completed in a single powerstroke. As an example, it is much more desirable to drive a staple ornail and to punch an opening in a single operation rather than to applyrepeated blows to the crown or head of the staple, nail or punchelement. In addition, the use of electrically operated tools over theextended periods of time required by repetitive power stroke operationpresents the substantial problem of dissipating the heat due to thelosses in the toolso as to keep the temperature of the tool low enoughfor manual use. i

To overcome some of the deficiencies in this type of equipment, a numberof single power stroke tools, both pneumatic and electric, have beendevised. The pneumatically operated tools have been satisfactory in manyapplications because of the large amount of power that can be suppliedto the point of impact with the work by using increased fluid pressureand larger piston diameters. These tools also do not encounter theheating problems of electrically operated tools. However, the necessityof providing a relatively high pressure source of compressed air orother pressurized fluid severely limits the range of use of pneumatictools to those applications in which the expected use is large enough toeconomically justify the expense ,ofproviding compressing facilities.These compressing facilities also are somewhat costly to maintain.

An electrically operated tool of the single power stroke 3,179,866Patented Apr. 20, 1965 ice type would have the advantage that electricpower is almost universally available and can be used as an energysource at a nominal cost. One approach to providing an electricallyoperated tool having a single power stroke is to use a rotating electricmotor to compress a spring that is subsequently released to drive thework engaging portion of the tool. However, the springs are subject tofatigue and the weight of the motor and linkage for stressing andreleasing the spring often makes the tool unwieldy for manual operation.In other types of devices, the driving force for actuating the tool isderived from an electromagnetically induced field acting on a magneticmember forming a part of the drive mechanism. However, it has beendiflicult to generatesufiiciently large magnetic fields with windingsenergized directly from the -120 volt lines commercially availablewithout using energy storing devices, such as capacitors. The size andweight of these components as well as the related control components isgenerally such that they cannot be mounted directly on a portable tooland require a separate housing, such as the ones shown in thecontemporaneously filed applications of Richard H. Doyle et al., SerialNos. 161,653 and 161,706, which applications are assigned to the sameassignee as the present application.

Accordingly, one object of the present invention is to provide a new andimproved electrically operated portable tool.

Another object is to provide a portable tool including new and improvedmeans for supplying electrical energy thereto.

A further object is to provide an electrically operated tool that isself-contained so as to be capable of easy, manual operation.

Another object is to provide a self-contained and electrically operatedportable tool which does not require energy storing means and which iscapable of delivering a large amount of output power.

Another object is to provide a portable tool of the single power stroketype including control means for supplying all the necessary operatingenergy during no more than a single cycle of an alternating currentpotential.

Another object is to provide a tool including a control circuit actuatedby manually operable switch means for supplying operating energy to thetool for no more than a single cycle of an alternating currentpotential.

Another object is to provide a control or operating circuit for a toolin which a manually actuated switch selects a single cycle or less ofalternating current energy for operating the tool.

In accordance with these and many other objects, one embodiment of theinvention comprises an electrically operated stapler or tackercomprising a portable, light?- weight housing having a chamber in whichan operating winding is disposed. A work engaging element, such as adriver blade, is provided with a magnetic portion disposed adjacent theoperating winding. The portable tool is connected to a source ofcommercially available alternating current potential by a flexible cableand includes a control circuit carried completely on or-within thehousing and connected between the cable and the winding. This controlcircuit includes a manually actuated switch means carried on the housingthat is efiective, when actuated, to select the first complete halfcycle of the alter nating current potential following the time at whichthe switch is actuated for energizing the winding to operate the tackeror stapler.

The control circuit includes a controlled conduction device, such as agated silicon rectifier, connected in series with the operating windingand an alternating current potential source. The gate or controlelectrode of the controlled conduction device is selectively connectedto a source of gating current under the control of the manually actuatedswitch through a second controlled conduction means. This secondcontrolled conduction means is placed in a conductive state to place thegated rectifier in a conductive condition at the beginning of and foronly the first positive-going half cycle of the alternating currentpotential that occurs following the manual actuation of the switchmeans. Thus, the operating winding is energized from the power sourcefor only a part of a cycle of the input alternating current potentialand is provided with an operating current of relatively large amplitudeto deliver a large amount of power to the workpiece. By directlyenergizing the operating winding from the alternating current potentialsource, the need for energy storing components, such as capacitors, isobviated with the result that all of the control components can becarried on the tool to provide a self-contained portable tool. Becauseof the extremely short duration that the operating winding is energized,the problem of excessive heating of the tool is obviated.

Many other objects and advantages of the present invention will becomeapparent from considering the following detailed description inconjunction with the drawing, in which:

FIG. 1 is an elevational view in partial section of a portable toolembodying the present invention; and

FIG. 2 is a circuit diagram of the controlled energy supply circuitincluded in the tool.

Referring now more specifically to FIG. 1 of the drawing, therein isshown a portable and electrically operated stapler or nailer, indicatedgenerally as 11), which embodies thepresent invention. The tackerincludes a non-magnetic housing 12 having a vertically extending forwardhead portion 12a defining a chamber 14 and a rearwardly extending hollowhandle portion 12b defining a cavity or chamber 16. An operating winding15% having a low resistance is disposed in the lower end of the chamber14 and includes an axially extending Opening in which is received thelower end of a magnetic plunger or core 22. A fastener driving blade 24is secured to the lower end of the magnetic plunger 22 and is adapted toengage and drive a fastener, such as a staple or nail, supplied by amagazine assembly indicated generally as 26. A tension spring 28connected between the core 22 and the housing 12 resiliently returns thecore 22 and the connected driver blade 24 to a normal position at theend of a cycle of operation.

To provide means for energizing or operating the tool '10, a flexiblecable 30 is connected between a conventional source of 60 cyclealternating current potential and a control circuit, indicated generallyas 32, that is carried on the tool 10 and disposed within the chamber 16in the hollow handle 12b. The control circuit 32 is connected to thewinding 18 and to a manually actuated switch 34 which is also disposedwithin the chamber 1e and which is actuated by a pivotally mountedtrigger 36. When the switch means 34 is actuated, the control circuit 32selects the first complete and properly polarized half cycle of thealternating current potential supplied over the cable 30 following theactuation of the switch means 34 and connects the winding 18 to thealternating current potential during this half cycle so that arelatively heavy current flows through the winding 18 for the durationof this half cycle. The duration of the current flow through the winding13 will be extended beyond a half cycle in some applications because ofthe inductance of the winding 13. The energization of the winding 18 bythis pulse of high energy and short duration produces a flux field thatacts on the magnetic core 22 to drive the blade downwardly to engage andset a fastener. After the termination of the half cycle and when theinduced field collapses, the core 22 and the blade 24 are restored totheir normal positions by the tension spring 28.

Although the physical construction of the electrically operated tackeror stapler 10 can be of any suitable design, the construction shown inFIG. 1 is similar to that of the electrically operated tacker shown anddescribed in detail in the contemporaneously filed application ofRichard H. Doyle et al. Serial No. 161,651, now Patent No. 3,141,171,which application is assigned to the same assignee as the presentapplication. This construction, however, has been modified to permit thecontrol circuit 32 to be mounted directly on the housing 12 of thetacker 1d so as to provide a completely self-contained tool It) that isboth portable and capable of supplying adequate power to perform afastener driving operation. The control circuit 32 can be formed in anydesired physical form, but preferably is formed on a suitable supportingmeans and then potted in one of the many well known compositionstherefor. In order to facilitate repair of the tool 11 it is desirableto removably mount the control circuit 32 on the housing 12 or withinthe chamber 16 in the hollow handle 12b. Accordingly, the upper wall ofthe handle portion 12b is provided with a removable closure element orplate 38 that is normally secured in position by removable fasteners(not shown) to close an opening iii. When the plate 38 is removed, thecontrol circuit 32 can be removed through the opening 40 and areplacement circuit inserted therein. This replacement of the controlcircuit 32 is facilitated by using detachable electrical connectors tointerconnect the circuit 32 with the other components of the portabletool 11).

More specifically, the control circuit 32 is provided with a pluralityof connectors or terminals 42 connected to the components in thecircuit. The housing 12 for the tool 19 and the housing for the switchmeans 34- are provided with a plurality of electrical connectors 44 thatare insulated from electric contact with the housing 12. The twoterminals 42 at the right end (FIG. 1) of the control circuit 32 engagetwo connectors 44 connected to the cable 30 to provide means forenergizing the circuit 32. The two connectors 54 on the switch 3 engagetwo terminals 42 at the left end of the circuit 32 to connect the switchmeans 34 with the control circuit 32, and the emaining two terminals 42on the circuit 32 engage a pair of connectors 44 connected to a cable 46to connect the control circuit 32 with the winding 18. By the provisionof the detachable terminals 42 and connectors 44, the control circuit 32can easily be replaced merely by removing the previous control circuit32 and inserting an additional one of these circuits.

FIG. 2 of the drawing illustrates the details of one control circuit 32that can be used to control the operation of the tool 111 or theenergization of the winding 18. In general, the circuit 32 controls theconductivity of a controlled conduction device, such as a gated siliconrectifier 60, to connect the winding 13 in series with the alternatingcurrent supplied over the conductors of the cable 30 for only the firstpositive-going half cycle of the input voltage occurring following themanual actuation of the switch means 34. A rheostat 62 connected inseries with one of the conductors of the cable 31) limits the currentthat can flow through the winding 18 and, thus, controls the energysupplied to the tool 11) during the half cycle in which the gatedrectifier 6th is in a conduction condition. The rheostat 62 can bemounted on the handle portion 12b of the housing 12 (FIG. 1) andincludes a manually actuated dial or knob 64 for adjusting the settingof the rheostat 62. This rheostat is connected in series between one ofthe electrical connectors 44 and one of the conductors of the cable 30.

In the normal condition of the control circuit 32, current flows througha voltage dividing network including a resistance element 66, a diode orrectifier 68, and another resistance element 70 during the positive halfcycles. The potential appearing across the resistor 70 is appliedthrough another diode or rectifier 72 to charge a capacitor 74 shuntedby a resistor 76. This potential is also forwarded through the diode 72and a pair of normally closed contacts 34a in the switch means 34 tocharge a capacitor 77. In this manner, the capacitors 74 and 77 arenormally charged to a potential determined by the value of theresistance elements 66 and 70. During the negative-going half cycles ofthe input alternating current potential, the charge on the capacitors 74and 7'7 discharges slightly through the shunting resistor 76 and thecollector-emitter circuit of a transistor 78 that is biased just aboveits cut-oif point. However, whenever the charge on the capacitors 74 and77 drops below the desired value, these capacitors are recharged throughthe diode 72 during the next following positive-going half cycle of theinput voltage.

' To provide means for controlling the periods of conductivity of thegated rectifier 60, a ditferentiating network including a capacitor 80and a resistance element 82 are connected across the resistance element70. The leading and trailing edges ofthe positive-going and basicallysquare wave generated across the resistance element 70 during thepositive-going cycles of input potential are differentiated to providepositive-going and negative-going pulses, respectively, which arecoupled directly to the base electrode of the transistor 78. Thepositive-going pulses corresponding to the leading edges of the squarewave occurring at the beginning of each positive-going half cycle of theinput alternating current signal increase conduction through thetransistor 78. This transistor operates as an emitter follower withcurrent amplification so that each positive-going input pulse applied toits base provides a corresponding positive-going output pulse across anemitter resistor 84. This positive-going output pulse tends to drive agate current through the gate electrode of a controlled conductiondevice, such as a gated silicon rectifier 86, the anode of which isconnected to the capacitors 74 and 77. However, the cathode of therectifier 86 is connected to an open circuit at a pair of normally opencontacts 34b included in the switch means 34. Thus, the rectifier 86normally cannot be placed in a conductive state. The control circuit 32remains in this condition until the switch means 34 is operated.

When the 'tacker 10. is to be operated, the trigger 36 is actuated tooperate the switching means 34. The operation of the switching means 34closes the normally open contacts 34b and opens the normally closedcontacts 34a. The opening of the contacts 34a interrupts the chargingpath for the capacitor 77 and disconnects the collector electrode of thetransistor 78 and the anode of the controlled rectifier 86 from allpotential sources except that provided by the charged capacitor 77. Theclosure of thecontacts 34b connects the cathode of the'controlledrectifier 86 tothe control electrode of the gated rectifier '60.However, the gated rectifier 86 is not placed in a conductive conditionat this time unless the alternating current potential supplied bythecable 30 is at the beginning of a positive-going half cycle. This istrue because an input signalis not provided at the base electrode of thetransistor 78 at any other time.

When the beginning of the next positive-going half cycle of thealternating current potential is reached, the differentiating networkincluding the capacitor 80 and the resistance element 82 supplies apositive-going pulse to the base of the transistor 78 so that thistransistor is .placed in a heavily conducting condition producing agpositive-going potential drop across the emitter resistance element 84.The drop across theresistance element .84 places the gate electrodeofthe controlled rectifier 86 at a positive potential relative to itscathode and places the gated rectifier 86in a conductive condition sothat the 6 capacitor 77 now discharges through the conductive tran:sistor 78 and the gated rectifier 86 into the gate or control electrodeof the gated rectifier 60 through the closed contacts 3411. This placesthe gated rectifier 60 in a conductive condition so that the winding 18is connected directly across the alternating current potential suppliedby the cable 30 in series with the rheostat 62. This energizes thewinding 18 to actuate the stapler or tacker 10.

At the end of the positive half cycle, the rectifier 60 lacks a properpotential across its cathode-anode circuit, and the rectifier 60 isrestored to a nonconductive condition. It the switch means 34 remains inan operating condition at the beginning of the next positive-going halfcycle of the applied alternating current potential, a positive'goingpulse is again applied to the base of the transistor 78. Thispositive-going pulse is not effective to initiate another period ofconduction through the gated rectifier 60 because the charge on thecapacitor 77 has been depleted and the components 78 and 86 lackcollector and anode potential. When the switch means 34 is released toclose the contacts 34a and to open the contacts 3412, any furtherconduction through the gated rectifier 86 is prevented by opening thecircuit to its cathode at the contacts 34b, and the charging circuit forthe capacitor 77 is established at the closed contacts 34a so that thiscapacitor is charged from the capacitor 74 and the alternating currentpotential supply. The control circuit 32 is conditioned for anothercyclet of operation.

Accordingly, the provision of the control circuit 32 makes possible theportable tool 10 which is electrically operated and which is completelyself-contained in requiring a connection to only a conventional sourceof alternating current potential. In view of the fact that the gatedrectified 60 can be placed in a conductive condition for only onepositive-going half cycle of the input signal following each manualactuation of the switch means 34, excessive heating of the winding 18and the tool 10 is avoided while providing adequate power to drive theblade 24. 7

Although the control circuit 32 can be fabricated with components ofmany different values and-types in accordance with the desired circuitapplication, one control circuit 32 using the following listedcomponents supplied the winding 18 with an operating current of between40 and 120 peak amperes persisting for a duration of around 8 /3milliseconds.

Gated rectifier 60 2Nl770 or 2N177OA. Rheostat 62 0-2 ohms.

Resistor 66 10K.

'Diode 6S Sarkes-Tarzian 2P4. Resistor 70 10K.

Diode 72 Sarkes-Tarzian 2P4. Capacitor 74 100 ,ufd.

Resistor 76 2.2K.

Capacitor 77 .47 ,lLfd- Transistor 78 2N1304 or 2N2l3. Capacitor 80 .01#fd.

Resistor 82 22K.

Resistor 84 2.2K.

Gated rectifier 86 2N1774.

Although the present invention has been described with reference to asingle illustrative embodiment thereof, it should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art that will fall within the spirit and scope of thisinvention.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

1. In a portable tool, a housinghaving a chamber, a winding disposed insaid chamber, work engaging means including a magnetic portion disposedadjacent said winding, a flexible cable connected to said housing andadapted to supply an alternating current potential to said tool, andcontrol circuit elements carried solely on said houssame es ing andconnected to said cable and said winding, said control circuit elementsincluding both a manually actuated switch means operable at random timesrelative to the alternating current potential and means controlled byactuation of said switch means and responsive to the polarity andamplitude of the alternating current potential for rendering no morethan one full cycle of said alternating current potential effective toproduce a flow of current through said winding to operate said tool sothat the tool is operated a single time independent of the length of theperiod during which the switch means is maintained in an operatedcondition.

2. The portable tool set forth in claim 1 in which said housing includesa hollow handle portion and in cluding means mounting said controlcircuit elements in said hollow handle portion.

3. A single stroke portable tool comprising a nonmagnetic housingforming a chamber, winding means disposed in said chamber, work engagingmeans movably mounted on said housing and including a magnetic portionpositioned adjacent said winding means, flexible cable means connectedto said housing for supplying an alternating current potential, manuallyoperable switching means carried on said housing, and control circuitelements carried on said housing and controlled by operation of saidswitching means for connecting the alternating current potential fromsaid cable to said winding for only the first one half cycle of saidpotential following the actuation of said switching means so that saidwinding is energized only during this half cycle to actuate said workengaging means through a single power stroke regardless of the length oftime that the switching means is held operated.

4. In a portable tool, a housing having a chamber, a winding disposed insaid chamber, work engaging means including a magnetic portion disposedadjacent said winding, a flexible cable connected to said housing andadapted to supply an alternating current signal to said tool, a manuallyactuated switch means carried on said housing, a controlled conductiondevice carried on said housing and connected in series with said windingand said cable, said controlled conduction device having a controlelectrode, and circuit means energized by the alternating current signaland carried solely on said housing, said circuit means including meansresponsive to the amplitude and polarity of the alternating currentsignal and the operation of said switch means for supplying an operatingsignal to said control electrode to place said controlled conductiondevice in a conductive state for only a portion of the duration of asingle cycle of the alternating current signal supplied to said tool bysaid cable, said circuit means preventing further conduction through thecontrolled conduction device until the switch means is released andreoperated.

5. In a portable tool, a housing having a chamber, a winding disposed insaid chamber, work engaging means including a magnetic actuating meansdisposed adjacent said winding, a flexible cable connected to saidhousing and adapted to supply an alternating current signal to saidtool, a first controlled conduction device carried on said housing andconnected between said cable and said winding to control theenergization of said winding, said controlled conduction device having acontrol electrode, a control circuit mounted on said cable and saidhousing and connected to said control electrode for selectively placingsaid first controlled conduction device in a conductive state, saidcontrol circuit including a second controlled conduction devicerequiring a unidirectional operating potential, means carried on saidhousing and energized by the alternating current signal from said cablefor supplying a unidirectional potential to said sec ond controlledconduction device, and manually operated switch means carried on saidhousing for controlling the operation of said control circuit.

6. A single stroke portable tool adapted to be energized by analternating current potential source comprising a portable housing,winding means in the housing, work engaging means having a magneticportion disposed adjacent the winding means, a flexible cable includingtwo conductors adapted to be connected between the alternating currentpotential source and the tool, manually actuated switch means carried onthe housing and operable at random times relative to the alternatingcurrent potential, a gated rectifier means carried on the housing andconnecting the winding means in series with the two conductors of thecable, said gated rectifier means having a gate electrode, and controlcircuit means coupled to the gate electrode and connected to andcontrolled by actuation of the switch means for placing the gatedrectifier in conduction to energize the winding means from thealternating current potential supplied by the cable for no longer than asingle cycle of the potential occurring fol lowing the random operationof the switch means, said control circuit means including means forinhibiting reinitiation of conduction through the gated rectifier untilthe switch means has been released.

7. The tool set forth in claim 1 in which the housing includes a hollowhandle portion and in which the control circuit means is disposed in thehollow handle portion.

8. An electric tool adapted to be energized by an alternating currentpotential source and controlled to provide a single power strokecomprising a portable housing having a chamber, winding means disposedin the chamber, work engaging means including a magnetic actuating meansmovably mounted adjacent the Winding means, a flexible cable connectedto the housing and including two conductors adapted to supplyalternating current voltage to the tool from the potential source,manually operable switch means carried on the housing and operable atrandom times relative to the alternating current potential, controlcircuit means connected to the two conductors to be energized by thepotential source and coupled to the unidirectional conducting means, andmeans connecting the switch means to the control circuit means, saidcontrol circuit means including means responsive to the time ofactuation of the switch means and the amplitude of the alternatingcurrent potential for placing the unidirectional conducting means inconduction for no more than one cycle of the alternating currentpotential for each actuation of the operable switch means.

9. An electric tool adapted to be energized by an alternating currentpotential source and controlled to provide a single power strokecomprising a portable housing having a chamber, winding means disposedin the chamber, work engaging means including a magnetic actuating meansmovably mounted adjacent the winding means, a unidirectional conductingdevice including a control electrode, a flexible cable connected to thehousing and adapted to supply alternating current voltage to the toolfrom the potential source, first circuit means in said housingconnecting the unidirectional conducting device and the winding means inseries with the potetial source over the flexible cable, control circuitmeans connected to the cable to be energized by the potential source andconnected to the control electrode to supply a control signal to thecontrol electrode capable of causing conduction through theunidirectional conducting device for no more than one cycle of thealternating current potential, a manually operable switch means carriedon the housing and operable between operated and released conditions,and second circuit means connecting the switch means to the controlcircuit means and effective to control the control circuit means todeliver a control signal to the control electrode during a selectedsingle cycle only of the alternating current potential supplied by theflexible cable and to prevent the delivery of another control signal tothe control electrode until the manual switch means has 9 10 beenoperated to its released condition and then returned 3,065,360 11/62Vallese 307-88.5 to its operated condition. 3,085,169 4/63 Abel 310-68FOREIGN PATENTS References Cited by the Examiner 242,179 10/62Australia.

UNITED STATES PATENTS 5 OTHER REFERENCES $323 General ElectricApphcatlons Bulletin 20( ).4-6/6l, 1 7 273 7 2 Weyondt 310 3 SCR g 9 PPP g 1 and P 4, Publlcatlon 1,678,979 7/28 Fox 310-30 10 June 1961-2,613,241 10/52 Weyondt 318-125 2,753,470 7/56 Armstrong 31O 17 M LT NHF E Primary Exammer- 3,018,383 1/ 62 Ellert 307--88.5 ORIS L. RADER,Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,179,866 April 20, 1965 Richard H. Doyle et al. I l I It is herebycertifiedthat error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 7, line 64, strike out "cable and said"; same column 7,- line 65,after "said" insert cable and said Signed and sealed this 24th day ofAugust 1965.

(SEAL) A nest:

ERNEST w. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 PatentNo. 3,179,866 April 20, 1965 Richard H. Doyle et al. I i It is herebycertified'that error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 7, line 64, strike out "cable and said"; same column 7, line 65,after "said" insert cable and said Sined and sealed this 24th day ofAugust 1965 (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attcsting Officer Commissioner ofPatents

1. IN A PORTABLE TOOL, A HOUSING HAVING A CHAMBER, A WINDING DISPOSED INSAID CHAMBER, WORK ENGAGING MEANS INCLUDING A MAGNETIC PORTION DISPOSEDADJACENT SAID WINDING, A FLEXIBLE CABLE CONNECTED TO SAID HOUSING ANDADAPTED TO SUPPLY AN ALTERNATING CURRENT POTENTIAL TO SAID TOOL, ANDCONTROL CIRCUIT ELEMENTS CARRIED SOLELY TO SAID HOUSING AND CONNECTED TOSAID CABLE AND SAID WINDING, SAID CONTROL CIRCUIT ELEMENTS INCLUDINGBOTH A MANUALLY ACTUATED SWITCH MEANS OPERABLE AT RANDOM TIMES RELATIVETO THE ALTERNATING CURRENT POTENTIAL AND MEANS CONTROLLED BY ACTUATIONOF SID SWITCH MEANS AND RESPONSIVE TO THE POLARITY AND AMPLITUDE OF THEALTERNATING CURRENT POTENTIAL FOR RENDERING NO MORE THAN ONE FULL CYCLEOF SAID ALTERNATING CURRENT POTENTIAL EFFECTIVE TO PRODUCE A FLOW OFCURRENT THROUGH SAID WINDING TO OPERATE SAID TOOL SO THAT THE TOOL ISOPERATED A SINGLE TIME INDEPENDENT OF THE LENGTH OF THE PERIOD DURINGWHICH THE SWITCH MEANS IS MAINTAINED IN AN OPERATED CONDITION.